Nanoscale physics 

Optical absorption in core-shell quantum antidot with donor impurity under applied co-directed electric and magnetic fields
Chubrei M. V., Holovatsky V. A., Holovatska N. H. 
Chernivtsi National University after Yuriy Fed’kovych. 
Kotsyubynsky, 2, Chernivtsi - 58012, Ukraine. 
E-mail: chubrei.maryna@chnu.edu.ua

The dependence of the energy spectrum on the size of nanoparticles, the effect of external fields, and impurity presence in nanoparticles give great potential for the practical application of quantum dots in optoelectronic systems such as light-emitting diodes and flat light-emitting panels, lasers, photodetectors, cells of solar panels and photoelectric converters. 
Theoretical studies of the co-directed electric and magnetic fields influence on an electron energy spectrum and wave functions are fulfilled in the multilayer spherical quantum dot (MSQD) Al0.3Ga0.7As/GaAs/Al0.3Ga0.7As with off-center donor impurity. The calculations were done within the effective mass approximation and the nanosystem rectangular potential profile by the matrix method using the exact electron wave functions in the nanosystem without the external fields and impurity effects [1]. In this paper it was investigated external fields combined effect and core size on the electron energy spectrum, binding energies of an off-center hydrogenic donor impurity and optical absorption coefficients.
For the electron energy spectrum, the ground state shifts to a lower energy region as the electric field strength increases. The magnetic field shifts all energy levels to a higher energy region. The magnetic field effect is stronger for larger nanostructures.
The linear a(1)(w), third-order nonlinear a(3)(I,w) and total optical absorption coefficients are defined by taking into account quantum transitions from ground to several excited states. The results show that external fields and impurity presence effects cause significant changes on the optical absorption coefficient. For nanosystems with a bigger core, the external fields effect is stronger. The absorption coefficients maximums shift to the region of higher energies with the increase of the magnetic field induction.

1.	Holovatsky V., Chubrey M., Voitsekhivska O. Effect of electric field on photoionisation cross-section of impurity in multilayered quantum dot// Superlattices and Microstructures. -2020.- 145.-P.106642.